There have been a few discussion over the last 36 hours about this. Most of it is inside baseball stuff, not political, but more about the mechanics of getting that loss to his personal return. A lot of it has to do with the magic of both creating basis in a particular kind of pass through entity, and then passing it through to Trump as an ordinary loss v. a capital loss.
Someone posted on twitter a transcript of an interview Trump did around that time, acknowledging that he walked away from the 3 casino bk’s owing about $950 million in personally guaranteed. Not that he walked away from the debt, he still owed it. And expected he would have it paid off it a short time.
What was posted was an original return, still subject to audit. Undoubtedly it was audited, and it’s very likely that this is what started his string of getting audited every single year, as this loss could have affected his return every year up to and including 2010.